


Myths Among the Mafia

by moonlightcarol



Series: Adoption Papers [2]
Category: Katekyou Hitman Reborn!, Percy Jackson and the Olympians & Related Fandoms - All Media Types, Percy Jackson and the Olympians - Rick Riordan
Genre: Alive Luke Castellan, BAMF Percy Jackson, BAMF Sawada Tsunayoshi, Do Not Mess With Mothers Here, Gen, Good Luke Castellan, Luke Castellan Has Mist Flames, Luke Castellan Redemption, Other Additional Tags to Be Added, Percy Jackson is Sawada Tsunayoshi's Other Lightning, Vongola Adopts The Jacksons
Language: English
Status: In-Progress
Published: 2020-12-04
Updated: 2021-01-23
Packaged: 2021-03-09 18:55:58
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 3,064
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27881114
Author URL: https://archiveofourown.org/users/moonlightcarol/pseuds/moonlightcarol
Summary: It takes one encounter to change everything and nothing at all. Myths should stay within its people but a certain mafia family doesn't know how to stay within the expected outcome.AKA the collection of one-shot about Percy Jackson x KHR crossover where Tsuna adopts or gets adopted by the casts in the other fandom.No. 2, An Overprotective Mist: Tsuna’s used to kidnapping attempts by now but not a boy he helped kidnapping him because he’s supposedly one of them. Or the one time, Tsuna’s Sky Flames led people to believe he’s a demigod.
Relationships: Luke Castellan & Sawada Tsunayoshi, Other Relationship Tags to Be Added, Percy Jackson & Reborn, Percy Jackson & Sally Jackson, Percy Jackson & Sawada Tsunayoshi, Sally Jackson & Sawada Nana
Series: Adoption Papers [2]
Series URL: https://archiveofourown.org/series/2024740
Comments: 10
Kudos: 175





	1. A Thieving Lightning

**Summary for the Chapter:**

> Percy doesn’t think that these so-called demigods should be surprised that he’s using a gun to fight off monsters…Reborn-sensei kills many monsters with his gun despite being a pure human and Tsuna-niisan even fights monsters with his gloves!

He didn’t want to be a half-blood.

Personally, he probably would be on board with the idea more if he hadn’t gone to Japan with his mother. Being a half-blood was dangerous and sometimes terrifying—something that could get him killed even—but it made life more exciting. It would have filled him with more achievements and feats than one would expect from people like him.

But that was before he met Tsunayoshi Sawada and his brand of craziness.

Now, he already had his life figured out and he didn’t need to have other things to consider. His mother was living her life now that she finally divorced with his stupid and scum of a stepfather. She even started a restaurant with her new best friend—a customer seemed to even catch her eyes.

And he, Percy Jackson, found the best brother in the world. Tsuna took care of him when his mother became too busy and led him to many interesting people, who never judged him for being him. The brunet didn’t bat an eyebrow for all the weird stuff that kept on happening to him—water just randomly appearing or being healed by water—and even tried to help Percy control his new found abilities.

It’s only thanks to Tsuna and his friends that he could defeat the sudden monster, which appeared out of nowhere. His mother got really scared at that time. She suggested to move but Tsuna’s scary tall tutor managed to convince him otherwise by killing shooting down a monster with one shot.

(Reborn definitely took reign of the training after Percy found himself being surrounded by green flames when Tsuna almost got hit by these monsters.)

Sally Jackson, his stunned yet grateful mother, explained all about the monsters that attacked them and his parentage.

“Your father is a god, Percy. That makes you a half-god.”

Not giving anyone the time to fully digest the information, a voice countered, “My absent husband’s a mafia, who forced our son to be a mafia boss.”

“Okaa-san!”

Tsuna frantically jumped over to his mother, who merely smiled—a terrifying smile if one asked Percy afterwards—and put his hand on top of her mouth to keep her from saying anything else. Sally watched the quick movement in stunned silence while the youngest person in the room couldn’t help but laugh.

In hindsight, the revelations actually seemed more serious than how the reaction went. Having a divine part in his blood made Percy a major target for monsters of all kind while Nana broke an omerta so the two Jacksons became honorary members of Vongola and the Vongola encountered creatures they never knew existed.

This simply vacation in Japan resulted into a permanent residency in Namimori—complete with the Jacksons finally escaping Smelly Gabe. It’s ultimately the best decision ever for the half-blood and his mother.

(Although, Sally did try to hit Reborn with a frying pan when the hitman revealed that he wanted Percy to be Tsuna’s second Lightning Guardian but that’s another story.)

Why was the son of Poseidon even reminiscing about this?

Percy repeated that he didn’t want to be a half-blood. He definitely did not want to even become involved with anything of his father’s side and he certainly did not want to run into couple of demigods in New York and be accused of stealing some fancy god symbol.

He was in a vacation, damn it!

_-0-_

Annabeth Chase widened her eyes, trying to comprehend how a smaller and defenseless boy had fished out a gun out of nowhere and easily shot down the three aggressive furies attacking them. Nico and Grover had ducked for over as soon as they heard the gunshots but they also stared at the demigod—because there was no way a mortal could have done that—singlehandedly destroyed three of the most powerful monsters in the Underground.

What surprised them even more other than the gun was the absolute control the boy had on the water surrounding him. The water had also mysteriously appeared out of nowhere when he gestured with his hands.

“Are you guys okay?” the boy asked, kneeling down on the two boys, who had sat on the ground when they ducked. He nervously scratched his cheeks at the distrustful and fearful way the three, especially the blond girl, looked at him. “Don’t worry. I’m not an enemy.”

Annabeth glared, not buying it, “It’s suspicious for you to step in right as we needed.”

“And that power…,” Grover started in astonishment but a sharp look from his female companion shut his mouth. He glanced at the black-haired boy in comprehensive silence.

Nico had stayed quiet since the young stranger had approached them but he also had a clue on what was going on with his companions’ mind. ‘He’s a child of the Big Three, just like me and Bianca,’ he concluded to himself. ‘Maybe he knows something about Lord Zeus’ Master Bolt?’

“I’m really not an—”

“Percy,” a voice called out and the boy blinked. He immediately straightened and lightened at the same time, a brown-haired teenager approached them, or rather the unknown demigod. “What’s going on?”

“Tsuna-nissan!”

‘Niisan?’ the three other half-bloods glanced at one another with Annabeth looking thoughtful at the unfamiliar word. “It’s Nihongo, I think?” she answered the obvious question before returning her attention to the pair of strangers.

“They were being attacked so I helped them out,” ‘Percy’ explained truthfully. “They’re like me.”

‘Tsuna-nissan’ didn’t blink when he said, “Demigods?”

He nodded and smiled proudly at the older boy as if wanting to be praised.

“You!” Annabeth shouted in anger, feeling out of her comfort because the boy only said ‘like me’ instead of ‘like us’ so the teenager was just a mortal. “You don’t tell mortals that!”

Frowning in confusion like he didn’t see what’s wrong, the boy named Percy stood in between them and the older teen protectively. “Tsuna-nissan is my family so of course, I would tell him,” he stated as a matter of fact.

“Well, you—"

The retort that the daughter of Athena was about to say got interrupted by a large creature appearing out of nowhere. It seemed like the monsters had tracked their smell and the girl gritted her teeth in annoyance and worry. They had not fully recovered from the battle earlier and now; they had a mortal to protect.

‘This is all his fault!’ she thought furiously, glaring at the water boy. ‘I am certain now. He’s definitely Poseidon’s son! How irritating!’

About shout in warning, the girl and her companions saw another lifechanging facts.

This so-called ‘Tsuna-nissan’ just went straight to the creatures surrounding them and calmed them down—even petting some of the more animalistic and smaller creatures. As for those creatures, who did ignore the brunet, a tall dark man suddenly appeared and killed them with a green gun.

“What did I just see?”

That was Nico voicing the right question.

(The three demigods almost wanted to faint when it was revealed that the two were both pure mortals without anything mythical going for them, unless one counted the dying will flames and Arcobaleno curse.)

* * *

**_Bonus:_ **

  * Nico had to appear earlier because it’s either him, Thalia or Jason, who could replace Percy’s role. Jason is out since he needs to be in Rome while Thalia is out because I had no idea how to legibly explain how she got out of being a tree.
  * In consequence, like how Sally is taken in canon, Bianca is taken by Hades…which confuses Nico when he’s revealed to be Hades’ son. I’m so not going into details with that. (Wait, does this mean that Nico should be going to Poseidon instead of Hades? …nope, just not gonna think of that plot hole there.)
  * Percy is Tsuna’s second Lighting guardian, who’s like five years younger than Tsuna and merely two years older than Lambo. Tsuna is so not amused at having children as his guardians…and in the same position, too!
  * Compared to Lambo, Percy oddly gets along with Gokudera well and he’s especially closest to Yamamoto after Tsuna. And yes, Percy and Lambo don’t get along despite Percy trying his best here.
  * Reborn can be a fantastic bodyguard for demigods if he ever quits being a hitman. Tsuna, on the other hand, is a great listener to rather sympathetic monsters. The others just fit being monster hunters.
  * Percy speaking curses and sometimes rough languages comes from being in contact with the other guys like the Varia. Sally is still very much angry at that while Tsuna tries hard to keep any more bad influences.
  * Sally and Nana are really bonding with how their absent husbands—even if Sally didn’t exactly marry Poseidon—forces their children into dangerous and troublesome lives.



**Notes for the Chapter:**

> I really should stop picking on picking Lightning Guardians...and I really do wonder why guns are not featured in Percy Jackson. Sure, swordfights are nice and all but we could use some variety of weapons, you know?


	2. An Overprotective Mist

**Summary for the Chapter:**

> Tsuna’s used to kidnapping attempts by now but not a boy he helped kidnapping him because he’s supposedly one of them. Or the one time, Tsuna’s Sky Flames led people to believe he’s a demigod.

Sawada Tsunayoshi knows that his life is chaotic. Having Reborn as his tutor makes it impossible to have anything but chaos thrown into his living. Being the Vongola Decimo—even before that and just merely being a candidate—gives nothing but troubles.

So, seeing monsters for the first time is sadly underwhelming.

“That’s a weird monster,” the boy thinks aloud, unfazed at the large bull-like man in front of him and sends him flying with a Flame-charged kick. He smiles in comfort at the fallen boy that the bull creature has tried to tackle. “Are you hurt?”

The taller blond, who looks the same age as him, stares wide-eyed at the flames coming out of his head. “Your head’s on fire,” he says frankly puzzled by what he’s seeing yet somehow, not overwhelmed. Tsuna has to blink. He’s taking this quite well all things considered, especially compared to other people not from Namimori—which has citizens being plainly desensitized or accepting all chaos in its path.

The brunet wonders if it has to do with the stranger being in the proximity of a monster and trying to fight it before Tsuna manages to save him. Maybe, the guy doesn’t even need his help, too…

“I’m fine,” the boy stands up and grins in gratitude at the brown-eyed boy, noticing the flames fading away. “That’s cool. Never seen a Hephaestus kid do stuffs like that.”

Hephaestus what? The sheer confusion must be obvious in his face because the taller boy’s grin fades into a contemplative frown.

“Wait, you do know that you’re a half-blood, don’t you?”

Tsuna briefly wonders if it means how he has Italian heritage because of his father, but his intuition says otherwise. He also looks too similar to her mother, appearing too Asian, except his gender for the other to consider that.

The blond boy looks alarm, especially when loud growls intensify. He bites his teeth, a heavy burden seeming to be overwhelming the former. Azure eyes flash in determination and he announces, “We need to get to the Camp!”

“I need to get you there quick!”

The moments that follow have the Vongola Decimo blinking and gaping at the taller teen. “Are you kidnapping me?” the absurdity of the situation almost makes him chuckle because this seriously seems to be a set up from Reborn. Or a rival famiglia may be acting up again.

But the young Sawada has just finished all his paperwork and last time he checks, the hitman’s on “Uni Guard” duty. He’s on break for once and he’s just trying to tour New York on his own without the mafia messing his day. No one even recognizes him as a mafia boss since he looks like a foreigner touring the city.

“Listen, I know that it will sound crazy,” the stranger—Tsuna really needs to get his name—mutters in a hurry as the presence of a deadly monster draws near them. He takes a tight grip on the smaller boy and the latter frowns, sensing something. “But you’re one of us. You’re a halfbood, a demigod. You have a parent’s that a god or goddess.”

Sawada Tsunayoshi freezes.

The first thing that comes into his mind is that he’ll kill Iemitsu for this.

_-0-_

After countless of thoughts on how to kill his father, the brunet realizes that for all his flaws, Iemitsu’s not a cheater. He appears so similar to his mother for them not to be related. His intuition highly agrees on that and the blond teen’s—Luke’s, he introduced himself as Castellan Luke, son of Hermes—statement doesn’t feel right for him. Tsuna has a feeling that there’s a misunderstanding going on here.

It’s also going to be hard to fix the misunderstanding, especially when he’s been dragged into the so-called camp now.

“I really think that you’re making a mistake,” the mafia boss tries. He really does try to stop the madness that the other is doing. Surely, it’s going to be complicated when people realizes that he’s no demigod. There must be some secrecy in all this myth business, especially when teens like Luke seem to be hunting monsters.

The jerk has the audacity to chuckle at his worries. “Don’t worry! You’ll be safe in the camp,” Luke smiles brightly with the slight edges. He seems to think of Tsuna’s worries as concern for monsters that would attack. “I’ll definitely protect you.”

The Sawada recognizes an issue when it’s right in front of him. The fact that unfamiliar Mist Flames clutch on his Sky Flames possessively and protectively gives him an idea of what’s going on.

Luke must have lost someone recently, probably a Sky and is on the edge of being discord. It’s alarming how no one knows an unbonded active Mist like Luke but that’s not the main problem. The problem is the blond has no idea about Flames and Tsuna just happens to accidentally court his Flames when he saves Luke moments ago.

Defenseless against a strong Sky courting his Flames, Luke probably feels the urge to stay with the mafia boss despite only meeting for the first time. This makes his thoughts be clouded and concludes a theory so that Tsuna will have to stay with him.

The brunet sighs heavily but he doesn’t deny the bond. It’s partially his fault after all and Tsuna thinks that Luke is a nice Mist all things considered. The taller demigod just wants to protect him and he really can’t hate Luke for that.

(Seriously, why is it always the Mist that causes him the most trouble? He thought that it’s already strange to bond with two Mists but now, he gets another one. Kami, he doesn’t even know how this will work. The meeting of the three Mists will most likely be very bad.)

(Tsuna wonders if he attracts and courts Mists weirdly. Mukuro attacks him and tries to possess him. Chrome helps him fight against elite assassin for their first meeting. Luke kidnaps him after he saves the blond.)

_-0-_

Luke Castellan has no idea what he’s doing. He’s not 100% certain that Tsuna is even a demigod as well but he wants the other to come with him. He doesn’t know why he feels like this. The blond boy has finally been offered a quest by his father. He’s finally able to prove himself worthy to be more.

He has a chance to prove that Thalia hasn’t died in vain; Luke is a demigod that will make her sacrifice to get them in Camp mean something. This quest has to be a success. He has no need for distractions.

And yet…

The son of Hermes looks at the innocent brunet in his arms. The boy has kicked a Minotaur to save him despite not knowing his name. He does all that, making his presence known to the monsters so that he saves Luke.

The fact strikes him to the core and he knows that he shouldn’t let go of a treasure like Tsuna.

He has already lost many of his loved ones for being a demigod. His mother, his father, Thalia…heck, Annabeth and Grover also count despite not being that close to them. He will admit to himself that he hates it.

Luke lives at the camp since they have arrived but he only feels like sinking into darkness, his experiences leaving him bitter and furious at the gods and Fate.

Then, Tsuna comes flying in and bringing a light that he has thought to be lost within him. He decides at that moment as the brunet smiles at him warmly, ‘He’s home.’

There’s no way he’ll let go.

(His Mist Flames rage despite feeling the other two Mist Flames already bonded on the powerful Sky Flames, “My Sky! He’s my Sky!”)

* * *

**_Bonus:_ **

  * Tsuna, despite his worries, is actually eligible to stay in Camp. He’s no demigod but he is Hestia’s legacy.
  * Luke got Flame rejected or scorned three times by now. His mother and father were no Skies but their actions left him feeling rejected. Thalia, his chosen Sky, actually accepts him despite not realizing all the flames stuff but we know what happened there. Coincidentally, if Tsuna didn’t get him first, I guess this means that he would have to be Flame-struck for Kronus, who seemed to be willing to accept him.
  * Hermes is going on “Suck Father” list that Tsuna has when Luke tells him of what happened to him as to why he hates gods and goddesses. All of those parent gods and goddesses might be on the list (Zeus, ironically, is second with Iemitsu as top one).
  * The meeting of the three Mists is disaster that no one wants to repeat, even Reborn who laughs at the idea of three Mists.
  * Mukuro is not liking how he has to share the Mist position with Luke and Luke just really thinks that the other Mist is too suspicious. They do both agree that Chrome is a goddarn good Mist and will be protected.
  * Reborn is living for all the chaos that his student is causing for being the first to have three equally powerful Mists and the whole myth thing.
  * Before you guys ask, I actually thought of making Luke either a Cloud or Rain. Rain, because I have headcannons that for all the Rain being the one to calm things, they kinda have major depressions like Yamamoto. Cloud, because they’re independent, I guess? I went with Mist because of the whole three Mist thing and Luke being a liar, deceiving everyone even himself.



**Notes for the Chapter:**

> Am I always going for the “saving the others from a monster as their first meeting” trope? I don’t know but it’s hilarious how many situations and reactions I can write about those type of meetings.


End file.
